eTable 1. Psoriasis Severity Questionnaire
eTable 2. Depression Screener Questions
eTable 3. Interaction Term Between Coronary Artery Disease and Psoriasis
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Cohen BE, Martires KJ, Ho RS. Psoriasis and the Risk of Depression in the US Population: National Health and Nutrition Examination Survey 2009-2012. JAMA Dermatol. 2016;152(1):73–79. doi:10.1001/jamadermatol.2015.3605
Psoriasis is a risk factor for depression. Depression may also trigger or exacerbate psoriasis. The relationship between psoriasis and depression, however, remains to be fully explored.
To investigate the association between psoriasis and major depression in the US population.
Design, Setting, and Participants
Population-based study using participants in the National Health and Nutrition Examination Survey from 2009 through 2012.
Main Outcomes and Measures
Diagnosis of major depression based on the Patient Health Questionnaire–9.
We identified 351 (2.8%) cases of psoriasis and 968 (7.8%) cases of major depression among 12 382 US citizens included in our study. Fifty-eight (16.5%) patients with psoriasis met criteria for a diagnosis of major depression. The mean (SD) Patient Health Questionnaire–9 score was significantly higher among patients with a history of psoriasis than those without psoriasis (4.54 [5.7] vs 3.22 [4.3], P < .001). Psoriasis was significantly associated with major depression, even after adjustment for sex, age, race, body mass index, physical activity, smoking history, alcohol use, history of myocardial infarction (MI), history of stroke, and history of diabetes mellitus (OR, 2.09 [95% CI, 1.41-3.11], P < .001). Interaction term analyses involving patients with a history of both psoriasis and a cardiovascular event, specifically MI or stroke, did not reveal a synergistically increased risk of major depression (psoriasis and MI: OR, 1.09 [95% CI, 0.28-3.60], P = .91; psoriasis and stroke: OR, 0.67 [95% CI, 0.12-3.66], P = .63). In adjusted multivariable models, the risk of major depression was not significantly different between patients with limited vs extensive psoriasis (OR, 0.66 [95% CI, 0.18-2.44], P = .53).
Conclusions and Relevance
Self-reported history of psoriasis was independently associated with major depression as assessed by a validated screening tool, even when controlling for comorbidities. History of cardiovascular event did not modify the risk of major depression for patients with psoriasis. The severity of psoriasis was unrelated to the risk of major depression. Therefore, all patients with psoriasis, regardless of severity, may be at risk for major depression.
Psoriasis is a chronic, systemic disease that affects between 3% and 4% of the US population.1 The psychological impact of psoriasis is substantial, since patients are at risk for a number of psychiatric conditions, including depression,2,3 anxiety,3,4 and substance abuse.4,5 A recent cohort study reported that the risks of depression and suicidal ideation were significantly higher in patients with psoriasis.3 Similarly, in a multicenter cross-sectional study investigating psychiatric conditions and various dermatological diseases, psoriasis demonstrated a significant association with depression and suicidal ideation.2
The identification of depression among patients with psoriasis is especially important given the association of major depression with decreased quality of life and increased all-cause mortality.6 Additionally, depression and psychological stress have been shown to potentially trigger or exacerbate psoriasis.7,8 The development of efficient depression screening tools, such as the Patient Health Questionnaire–2 (PHQ-2), allows accurate screening of major depression to take place within minutes, making screening feasible in the outpatient setting.9
Recognizable risk factors for major depression in patients with psoriasis have not been fully elucidated. For instance, the relationship between the severity of psoriasis and risk of psychiatric illness is conflicting in various reports.3,8,10,11 Kurd et al3 reported that the risk for depression was higher in patients with severe psoriasis compared with those with mild psoriasis. Several other studies have not found an association between severity of psoriasis and depression.8,10,11
Studies have shown that both depression12-14 and psoriasis15-17 are associated with cardiovascular disease. Therefore, a history of cardiovascular disease may confound the relationship between psoriasis and depression. The majority of prior studies, however, have not comprehensively investigated the complex relationship that may exist between psoriasis, cardiovascular disease, and depression. In this study, we sought to investigate the relationship between psoriasis and major depression in a nationally representative, population-based cohort, after adjusting for multiple cardiovascular risk factors. To our knowledge, this is the first study examining such an adjusted association between psoriasis and depression in a cohort representative of the US population.
The institutional review board of the New York University School of Medicine granted approval of this study under the classification of non–human subject research. Informed consent was waived, as the data used were nonidentifiable and publicly available.
This study was conducted using publicly available data from the National Health and Nutrition Examination Survey (NHANES), a cross-sectional survey administered by physicians and highly trained medical personnel comprising questionnaires, physical examinations, and laboratory data. The aim of NHANES is to determine the prevalence and risk factors of major diseases in the US population. The National Health and Nutrition Examination Survey biannually releases data collected from participants located across the United States selected using a complex, multistage, stratified sampling method that has been shown to produce a cohort that is representative of the US population.18
We examined the most recently available surveys collected from 2009 through 2012, which include specific questions regarding psoriasis history and a depression screening tool. All adults (≥18 years) who responded to questions regarding psoriasis history were included in our analysis. In the NHANES data set, certain populations, such as those older than 60 years, African Americans, and Hispanics, are oversampled to adjust for inconsistent response rates and variable selection probabilities between subgroups. This is done in order to produce a nationally reflective cohort.
History of psoriasis was determined by a questionnaire in which patients responded “yes” or “no” to the question, “Have you ever been told by a doctor that you have psoriasis?” A subset of patients with psoriasis was asked to rate the extent of psoriatic lesions on a 1 to 4 scale. Patients responded to the question, “Do you have little or no psoriasis (1), only a few patches that could be covered by 1 or 2 palms of your hand (2), scattered patches that could be covered with between 3 and 10 palms (3), or extensive psoriasis covering large areas that would be more than 10 palms of your hand (4)?” (eTable 1 in the Supplement). In our analyses, this variable was dichotomized to “limited” (response of 1 or 2) or “extensive” psoriasis (response of 3 or 4).
The depression screener was composed of the 9 questions from the Patient Health Questionnaire–9 (PHQ-9) depression assessment tool. Patients were asked to score each of the 9 criteria for the diagnosis of major depression present in the Diagnostic and Statistical Manual of Mental Disorders, fourth edition (DSM-IV), on a 0 to 3 scale depending on the frequency of symptoms. Patients were asked, “over the last 2 weeks, have you been bothered by the following problems: little interest or pleasure in doing things, feeling down/depressed/hopeless, trouble sleeping or sleeping too much, feeling tired or having little energy, poor appetite or overeating, feeling bad about yourself or that you are a failure, trouble concentrating on things, moving or speaking slowly or too fast, thoughts that you would be better off dead or hurting yourself in some way?” (eTable 2 in the Supplement). Participants chose 1 of the following responses to each of the 9 questions: “not at all” (score of 0), “several days a week” (score of 1), “more than half the days” (score of 2), or “nearly every day” (score of 3). In our analyses, a diagnosis of major depression was considered if the summed score on the PHQ-9 was greater than or equal to 10 points. The use of a PHQ-9 score cutoff of 10 points has been shown to offer a favorable balance between sensitivity and specificity.19
Suicidal ideation was considered if participants responded “yes” to the question, “Have you had thoughts that you would be better off dead or hurting yourself in some way?” for several days a week or more. All patients were also asked to rate the extent to which depressive symptoms interfered with daily functioning. Patients were asked, “How difficult have these problems made it for you to do your work, take care of things at home, or get along with people?” Patients responded as “not at all difficult,” “somewhat difficult,” “very difficult,” or “extremely difficult.” In our analyses, this variable was dichotomized to “no daily functional impairment” (“not difficult”) and “daily functional impairment” (“somewhat difficult,” “very difficult,” or “extremely difficult”).
Body mass index (BMI) (calculated as weight in kilograms divided by height in meters squared) was obtained from data collected during a physical examination attended by each participant. To assess physical activity, patients selected whether they engaged in no physical activity, moderate physical activity, or vigorous physical activity. Specifically, patients were asked, “Do you do any sports, fitness, or recreational activities that cause a large (vigorous physical activity) or small (moderate physical activity) increase in breathing or heart rate?” Smoking history was determined if the patient responded “yes” to ever smoking at least 100 cigarettes. Significant alcohol use was determined by the question, “Have you ever had 4 (for women) or 5 (for men) or more drinks every day?” Covariates relating to medical history such as a history of myocardial infarction (MI), coronary artery disease (CAD), stroke, and diabetes mellitus (type 1 or type 2) were gathered from specific, individual questions asking participants whether a physician had ever told them that they had the condition of interest.
We used t tests to analyze continuous variables and the χ2 test for categorical variables for univariate analyses. Multivariable logistic regression models were constructed to examine the relationship between the exposure and outcome of interest after adjustment for age, sex, race, BMI, physical activity, smoking, alcohol use, and history of MI, stroke, and diabetes, unless otherwise specified. In multivariable models, race, BMI, and physical activity were analyzed as categorical variables with more than 2 categories. Interaction analysis was performed with an interaction term examining patients with both a history of psoriasis and a history of stroke, MI, or CAD. SPSS statistical analysis software, version 22.0 (SPSS Inc), was used to analyze study data using the complex survey function for the NHANES population data. All statistical tests were 2 tailed, and the significance level was set at P < .05. Multiple comparisons for categorical variables with more than 2 categories were adjusted using the Bonferroni correction.
Our final data set comprised 12 382 patients. We identified 351 cases (2.8%) of psoriasis and 968 cases (7.8%) of major depression (PHQ-9 score ≥ 10). Compared with patients without psoriasis, those with psoriasis were older, had a higher mean BMI, and more commonly reported a history of smoking, CAD, MI, and diabetes (Table 1). The mean (SD) PHQ-9 score was significantly higher among patients with a history of psoriasis than those without psoriasis (4.54 [5.7] vs 3.22 [4.3]; P < .001). Univariately, psoriasis was also significantly associated with major depression (16.5% vs 8.9%; P < .001) (Table 1). This association persisted in the multivariable model after adjustment for sex, age, race, BMI, physical activity, history of smoking, alcohol use, MI, stroke, and diabetes mellitus (OR, 2.09 [95% CI, 1.41-3.11]; P < .001) (Table 2). Other significant independent risk factors associated with increased odds of depression were older age (OR, 1.02 [95% CI, 1.01-1.02]; P < .001), smoking history (OR, 1.78 [95% CI, 1.49-2.13]; P < .001), significant alcohol use (OR, 2.76 [95% CI, 2.27-3.35]; P < .001), history of MI (OR, 2.24 [95% CI, 1.55-3.25]; P < .001), history of stroke (OR, 1.83 [95% CI, 1.26-2.67]; P = .002), history of diabetes (OR, 1.81 [95% CI, 1.42-2.29]; P < .001), and BMI between 30.0 and 34.9 as compared with BMI less than 25.0 (OR, 1.52 [95% CI, 1.04-2.20]; P = .02). Protective factors were male sex (OR, 0.37 [95% CI, 0.31-0.44]; P < .001) and participation in physical activity (moderate as compared with no physical activity: OR, 0.58 [95% CI, 0.47-0.96]; P = .01; vigorous as compared with no physical activity: OR, 0.42 [95% CI, 0.35-0.50]; P = .002) (Table 2).
In our cohort, there were 26 patients who endorsed a history of both MI and psoriasis and 16 patients with both psoriasis and stroke. Whereas a history of psoriasis, MI, or stroke each individually demonstrated a significant association with a risk of major depression, interaction analyses did not reveal a statistically significant additive risk for the participants with a history of both psoriasis and MI (OR, 1.09 [95% CI, 0.28-3.60]; P = .91) or psoriasis and stroke (OR, 0.67 [95% CI, 0.12-3.66]; P = .63) (Table 2). The effect of a history of CAD on the relationship between psoriasis and major depression was also investigated because this would encompass a greater percentage of patients compared with the narrower end point of MI. However, after replacing participants who reported a history of MI with those who reported a history of CAD, the interaction term for a history of both psoriasis and CAD in the multivariable model was similarly not significant (OR, 0.22 [95% CI, 0.03-1.82]; P = .15) (eTable 3 in the Supplement).
More patients with psoriasis (23.6%) reported that any symptoms of depression caused significant daily functional impairment, compared with patients without psoriasis (15.4%) (P = .004). This association persisted in multivariable models (OR, 1.44 [95% CI, 1.03-2.00]; P = .03) (Table 3). More patients with psoriasis (4.9%) reported suicidal ideation than those without psoriasis (3.7%). However, this univariate relationship was not statistically significant (P = .28) (Table 1).
The prevalence of major depression was not significantly different in patients with limited psoriasis compared with extensive psoriasis (18.4% vs 23.1%; P = .59). Our multivariable model similarly did not show a significant association between greater extent of psoriasis and major depression risk (OR, 0.66 [95% CI, 0.18-2.44]; P = .53) (Table 4).
Our results suggest that patients with psoriasis are at increased risk for depression. In our cohort, the prevalence of major depression among patients with psoriasis was 16.5%, which is in accordance with the results of a recent meta-analysis reporting a prevalence of 9% to 28%.20 Several prior studies have supported this association.2,3,7 Kurd and colleagues3 performed a population-based cohort study in the United Kingdom examining the risk of depression, anxiety, and suicidality in patients with psoriasis. The authors found that there was an elevated risk of depression, anxiety, and suicidality. In a multicenter cross-sectional study investigating psychiatric morbidity and various dermatological diseases, Dalgard et al2 found a significant association between depression and psoriasis. In that study, psoriasis was the only disease significantly associated with suicidal ideation, and the majority attributed their suicidal thoughts directly to their psoriasis. Whereas we found a numerically higher rate of suicidal ideation in our cohort among patients with psoriasis, this difference was not statistically significant. However, patients with psoriasis in our study were significantly more likely to report that any of their symptoms of depression interfered with daily functioning.
Few studies have examined the risk of depression in patients with psoriasis while controlling for comorbidities. In our study, a significant relationship persisted even when we controlled for confounding variables, including age, sex, race, BMI, physical activity, smoking, significant alcohol use, and history of chronic diseases such as MI, stroke, and diabetes mellitus. A number of studies have reported an association between depression and cardiovascular disease, such as MI or stroke.12-14,21 There are a number of proposed mechanisms for this association including biological, genetic, and behavioral factors.21 We investigated the possibility that a history of MI or stroke modifies the relationship between psoriasis and depression; however, the interaction term was not significant. We initially investigated the interaction between psoriasis and MI because it has been demonstrated that the risk of depression is more strongly associated with a history of MI than CAD.12 However, even when we replaced participants who reported a history of MI with the larger sample of participants who reported a history of CAD, the interaction term between psoriasis and a history of CAD was similarly nonsignificant. We are unaware of prior studies examining the risk of depression in patients with psoriasis after accounting for factors associated with cardiovascular disease risk or history of cardiovascular events. One study reported a significant risk of psoriasis in patients with depression after adjusting for obesity, diabetes, dyslipidemia, and hypertension. However, this relationship was not explored in the reverse direction.22
We found that the risk of major depression was unrelated to the severity of psoriasis. In accordance with our findings, Pacan and colleagues8 reported that there were no significant differences in the Psoriasis Area Severity Index scores of patients who received a diagnosis of depression on the basis of psychiatric examination or through the Beck Depression Inventory. Similarly, a survey study by Bangemann and colleagues11 reported that psoriasis severity or physical discomfort was not related to the risk of depression or anxiety. In contrast, Kurd et al3 reported that the risk of depression was higher in patients with severe compared with mild psoriasis, and Gupta et al23 found that the rate of suicidal ideation was correlated with self-reported psoriasis severity.
The psychiatric burden of psoriasis may be more closely tied to patients’ perception of the social response to their appearance than objective disease severity.10,24,25 In a study of 204 patients attending a psoriasis specialty clinic, reductions in quality of life were most strongly associated with the stress of anticipating a negative reaction by other people.24 In another study of 100 patients, the majority of patients reported that the most challenging aspect of the disease was the concern of feeling embarrassment related to their appearance.25 In accordance, Perrott and colleagues10 showed that physician-rated psoriasis severity was a poor predictor of patient scores on quality of life and stigmatization scales.
Limitations to our study include use of a cross-sectional survey, preventing us from establishing a temporal relationship between depression and psoriasis. Furthermore, the depression screening questionnaire in NHANES asks about symptoms within the prior 2 weeks, while questions regarding psoriasis within NHANES do not specify a timeframe of diagnosis. This likely underestimates the degree of correlation between depression and psoriasis in this study. In addition, we used self-reported questionnaires, making our data susceptible to recall and information biases. We were limited by the available data and were unable to control for particular variables such as sexual dysfunction, which has been linked to both psoriasis26 and depression.27 Similarly, we were unable to determine the location of psoriatic lesions, which may confound the relationship between psoriasis severity and the risk of depression. Finally, in our interaction term analysis, there were few patients with a history of both psoriasis and a cardiovascular event in our cohort, which may not yield sufficient power to detect a difference.
The study has a number of strengths. To our knowledge, this is the first study using a nationally representative cohort to examine the association between psoriasis and major depression. We analyzed a large, nationally representative sample of patients and were able to control for a large number of variables. The reliability of self-reports of various dermatologic and nondermatologic medical conditions has been demonstrated to be satisfactory.28-32 Patient self-report of psoriasis severity was shown in a prior study to be valid and reliable using a psoriasis severity questionnaire.33 Additionally, our definition of depression was based on a well-validated instrument for the diagnosis of major depression using criteria from the DSM-IV.34
Self-reported history of psoriasis was independently associated with major depression as assessed by a validated screening tool. Participants with psoriasis were more likely to report that any depressive symptoms interfered with work and social functioning. Whereas a history of cardiovascular events was associated with depression, a history of cardiovascular events did not modify the risk of major depression for patients with psoriasis. The risk of major depression was not associated with the self-reported degree of psoriasis. Therefore, our study supports that all patients with psoriasis, regardless of severity, are at risk for depressive symptoms and may benefit from depression screening.
Accepted for Publication: August 16, 2015.
Corresponding Author: Roger S. Ho, MD, MS, MPH, The Ronald O. Perelman Department of Dermatology, New York University School of Medicine, 240 E 38th St, 12th Floor, New York, NY 10016 (firstname.lastname@example.org).
Published Online: September 30, 2015. doi:10.1001/jamadermatol.2015.3605.
Author Contributions: Mr Cohen had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.
Study concept and design: All authors.
Acquisition, analysis, or interpretation of data: All authors.
Drafting of the manuscript: Cohen.
Critical revision of the manuscript for important intellectual content: All authors.
Statistical analysis: All authors.
Study supervision: Martires, Ho.
Conflict of Interest Disclosures: None reported.